What You Need to Know About Coil Thread Inserts

When you use threaded fasteners, you’re bound to run into situations where the threads are stripped or need reinforcing because the material is too soft. That’s when you need to consider coil thread inserts.

Coil thread inserts are underappreciated; they repair stripped holes in softer materials and reinforce fasteners used to bind softer substrates. Coil thread inserts are essential for threaded fasteners in wood, aluminum, plastics, and other materials that can’t securely hold a threaded fastener. 

What Are Coil Thread Inserts? 

A coil thread insert, also called a helical coil insert, is a coiled wire used to reinforce drill holes. Once inserted in the hole, the coil accepts a threaded insert, such as a bolt. The bolt’s outward pressure presses the coil against the sides of the hole, forming a firm bond.
 
Coil thread inserts are extremely reliable and create a strong, lasting joint, especially in softer materials. Most are cold-formed and made from rolled steel, nickel, or other materials chosen for their strength, performance in high-temperature environments, resistance to corrosion, and other characteristics.

Coil thread inserts are the go-to solution to fix stripped threads, such as in an engine block or any hole that uses threaded bolts. Once the coil thread is in place, the bolt can be installed and removed without concern for stripping the threads.

Coil thread inserts are used for various aerospace, automotive, electronics, manufacturing, transportation, and construction applications. They are ideal for reinforcing and repairing threaded joints that must be disassembled regularly.

Installing Coil Thread Inserts

You install coil thread coil inserts much like you do any other fastener. You start with a screw tap insert to either create a new hole or prepare an existing one to make a screw thread that will accept the insert. You can use a go/no-go gauge to ensure the thread pitch is correct throughout the hole.

Choosing the right size insert for the hole is essential for lasting, reliable performance. The proper size includes the insert’s diameter and depth to ensure it fits the hole.
 
You can insert thread coil inserts using manual or power tools. They screw in like any other threaded fastener. You can choose between free-running coils or screw-lock coils. Free-running insert coils distribute the load evenly across the hole and the bolt.  

Screw-lock coil inserts are designed to hold bolts under pressure or vibration. In addition to pressing against the sides of the hole, the screw-lock insert includes an internal locking thread that flexes to bite into the hold and keep the bolt in place.

Tanged vs. Tangless Coil Inserts 

There are two basic types of thread coil inserts—tanged and tangless coil thread inserts—with different designs to accommodate installation. 

Tanged coil inserts use a straightened piece of metal that extends across the diameter of the insert. The installation tool grips the tang to screw the coil into place. Once the coil is installed, the tool snaps off the tang to complete the installation.

Tangless coil inserts have a notch at the end of the coil rather than a tang for the installation tool to grip. Installation is done the same way but without snapping off the metal tang to set the coil inserts.

Tangless thread coil inserts have been gaining in popularity for several reasons:

• They’re faster to install and easier to inspect.
• They can be adjusted after installation.
• They don’t leave foreign metal that can create a hazard or ruin machinery.

Leading Coil Insert Manufacturers 

The Bay Supply Marketplace has a variety of thread coil inserts from different vendors. Here are just four to consider:

E-Z Lok

E-Z Lok is one of the few companies that specialize in threaded inserts. The company began by making threaded inserts for the airline industry to mount aluminum panels and parts. Since then, it has expanded to develop inserts for virtually any application, from making furniture to building retail displays. The company is seeing growth in emerging applications such as 3D printing and injection-molded plastics. Its E-Z Coil inserts are especially popular.

STANLEY Engineered Fastening

Heli-Coil^® wire threaded inserts from STANLEY Engineered Fastening come in different configurations, including various materials and plating. They’re used in the automotive, manufacturing, defense, aerospace, and related industries and are available in locking and nonlocking, tangent, and tangless designs.

Kato Fastening Systems

Kato Fastening Systems makes both the tanged and tangless CoilThread inserts designed for permanent, wear-resistant applications. CoilThread inserts are made of cold-rolled stainless steel wire, stainless steel alloys, phosphor bronze, and other materials.

Arconic Fastening Systems

Arconic Fastening Systems makes the Recoil thread inserts, which come in tangless and tanged free-running inserts in stainless steel, steel alloys, and phosphor bronze. Recoil inserts are also available in silver, cadmium, tin plating, and dry film lubricants. They are used in the automotive, shipbuilding, power generation, manufacturing equipment, consumer electronics, aerospace, and transportation industries.

There is a lot more you should know before choosing the best thread coil insert for your next job. To learn more, download our The Essential Guide to Coil Thread Inserts and shop for coil thread inserts on the Bay Supply Marketplace.